An upcoming book about George Harrison's life will reveal darker secrets about the late Beatles guitarist, including rifts with Paul McCartney and how being in the band nearly sent him spiralling into a nervous breakdown.

Graeme Thomson, author of George Harrison: Behind the Locked Door, spoke those who knew Harrison best, including ex-wife Pattie Boyd and close friend Roger McGuinn of The Byrds.

Glyn Johns, who produced the band's final album Let It Be, revealed Harrison wanted to quit the band during the recording after rows with bandmate Paul McCartney. "It was very uncomfortable," said Johns in The Daily Mail. "To watch this begin and be there in the immediate aftermath was very unpleasant."

Paul McCartney and George Harrison in 1964

Former model Patti Boyd, who was married Harrison from 1966 to 1977, confirmed their fractious relationship.

"George saw Paul as difficult," she said. "They would tolerate each other, but I think George basically didn’t like Paul’s personality. I just think they really didn’t love each other."

As the band's fame escalated, it is claimed that Harrison escalated into a spiral of paranoia, fearing he would be shot. This fear still remained even a decade later, when Harrison had gone solo. David Acomba, who filmed Harrison's 1974 solo tour, said: "George was constantly worried about being shot".

Harrison enjoyed a long and prolific solo career after the end of the Beatles, and found happiness in his conversion to Hinduism. He died in 2001 after battling lung cancer.

‘George Harrison: Behind The Locked Door’ by Graeme Thomson is out now.